Germany and the United States have renewed calls for Liu Xia, widow of China’s most prominent human rights dissident Liu Xiaobo, to be released from house arrest and allowed to travel overseas, as hopes fade that she will be able to leave the country.

The 57-year-old has been under house arrest since 2010, but has never been charged with any offence by the Chinese authorities.

Overseas appeals for her release peaked in July last year after her husband, a Nobel Peace Prize winner in 2010, died of liver cancer in custody.

The calls from Germany and the US are the first from Western governments in more than six months, after speculation in January that Liu might be permitted to leave China soon.

“We are hoping for a swift, positive conclusion of her case,” Germany’s ambassador to China, Michael Clauss, told the South China Morning Post in an exclusive interview.

“We hope that Liu Xia can finally enjoy freedom of movement and to travel wherever she desires. This has been a continuously stated concern of Germany for a long time already, just like the fact that she is welcomed to Germany if that remains her wish,” Clauss said.

“A positive solution of her case becomes more and more urgent as time passes,” he added.

Jinnie Lee, a spokeswoman for the US embassy in Beijing, said in a statement that Washington remained deeply concerned about the health and well-being of Liu.

“The United States continues to call on Chinese authorities to remove the restrictions on Liu Xia’s movement and communications, and allow her to leave China, if she so wishes,” Lee said.

The remarks came after the US published its annual human rights report on Sunday, calling China, Russia, Iran and North Korea “forces of instability”. It also said that Beijing was responsible for arbitrary detentions, executions without due process and coerced confessions of prisoners, as well as forced disappearances.

In January, there was optimism that Liu might be granted full freedom after a number of high-profile pro-democracy activists said she could be released soon, citing Chinese government sources.

Some of her friends believed this could happen after Beijing concluded important annual meetings of the legislature and political advisory body in March.

But with no recent progress, observers now say that it is unlikely her situation will change any time soon.

Steve Tsang, director of the SOAS China Institute at the University of London, said there had not been any indication that President Xi Jinping would soften his stance on the case.

“I should think not ... [She is expected to] attract a good bit of media coverage and may potentially become a rallying point for Chinese dissidents overseas,” Tsang said. “Why would Xi allow that to happen?”

Meanwhile, people who have had regular access to Liu confirmed that she was still under house arrest.

The authorities have not given any indication that Liu could be allowed to leave China, and the Ministry of Foreign Affairs has repeatedly told reporters that she “enjoys all freedoms in accordance with the law” as other Chinese.

The ministry was not immediately available for comment on Thursday.

But the Post has learned from sources that Liu’s case was “well beyond the control of the Ministry of Foreign Affairs or the Ministry of Public Security”.

“It is actually being managed at a higher level,” according to a source with direct knowledge of her situation.

The severe restrictions on Liu’s freedom were “badly damaging Beijing’s efforts to acquire soft power in international relations”, according to Jerome Cohen, a leading expert on Chinese law and government at New York University School of Law.

Rising nationalist sentiment between China and the US also makes a compromise on human rights more unlikely.

“We need only recall that Zhao Ziyang, the leader of the Chinese Communist Party until the June 4 crisis in 1989, was himself required to spend the last 16 years of his life under lawless house arrest,” Cohen said.

“But the situation seems to have become worse under the Xi Jinping government. Only an upsurge of world protest can enable Liu Xia to gain her freedom,” he said.

Richard Bush, co-director of the Centre for East Asia Policy Studies at the Brookings Institution, said that “Liu Xiaobo and, by extension, Liu Xia, symbolise something that the CCP regime hates and fears”.

He believed resolving the case would not help to ease diplomatic pressure on Beijing in a way that could improve trust between China and Western powers.

“And even if it did, the effect would not last very long,” Bush said.

Tsang was equally pessimistic about Liu’s plight.

“In any event, I don’t see it being resolved. Xi is not prepared to be lectured by Europeans on human rights,” Tsang said.

Liu Xiaobo died aged 61 in a Liaoning hospital on July 13, becoming the first Nobel Peace Prize winner to die in custody since German pacifist Carl von Ossietzky in 1938. He was awarded the prize in 2010 while in jail and was represented by an empty chair at the ceremony in Oslo.

He was jailed for 11 years in 2009 on subversion charges after co-authoring a petition known as Charter 08 calling for sweeping political reforms in China.

In June before Liu Xiaobo’s death, his wife, friends and members of the international community unsuccessfully appealed to Beijing for the dissident to be allowed to go overseas for medical treatment.

Liu Xia’s friends have said she has been cut off from the outside world since her husband’s death, and is taking medication for depression.